Crispy Potato-Wrapped Salmon

Yield:	1 Servings
Categories:

1	lg	Russet potato
2		9-ounce pieces center-cut salmon filet, skinned
		Vegetable oil for frying
1	bn	Spinach (about 3/4 pound); stems discarded
3/4		Stick (6 tablespoons) plus 1 teaspoon cold unsalted butter, cut into bits
2	ts	Fresh lemon juice
1	ts	Water
2	ts	Whole-grain mustard